Many neurological deficits and disease entities involve difficulties in visual space perception and visually guided behavior, and may involve fine manual control and/or gross motor behavior. Central to these losses is the ability to orient and localize things in space relative to oneself )'egocentric visual localization and orientation'). The proposed research will involve experiments aimed at delineating the mechanisms controlling emphasis on the visual perception of elevation, visual perception of orientation within the frontal plane, and the perception of visual pitch. A distinguishing aspect of the approach is the reduction of large visual influences on the perceptions of location and orientation to influences arising from individual straight lines and their combinations. These influences exert effects on both where things are perceived and where pointing and reaching behavior locates them. Considerable success has already been achieved with this approach. In addition, several of the aspects of the program are concerned with influences from other sources on these dimensions, including extraretinal inputs from vestibular, somesthetic, proprioceptive, and command (efference-generating) systems, and with interactions between the influences from these sources and the visual influences on perceptual and manual localization. The proposed work consists of five segments, the first three of which will explore our two theoretical models which (a) explain our recent discoveries of distance-contingent errors in manual pointing, reaching, and height matching for targets that are perceptually mislocalized due to the orientation of individual straight lines in the visual field, and (b) explain our discovery of a one-sided induction function for binocular depth contrast generated by a single inducing line. The fourth segment will measure the temporal development of changes in localization and orientation (dynamics) in the dimension of perceived elevation, and the fifth segment will search for commonalities and differences in the combining rules, gaze dependence, around-the-clock orientation functions involved in the mechanisms for controlling the perception of elevation and the perception of orientation in the roll-tilt dimension. As a special case of the last segment we will search for nonlinearities in the rule by which the 'frame' is composed from its line segments.